Wide belt abrasive machine



Nov. 28, 1967 P. J. ROEHRIG WIDE BELT ABRASIVE MACHINE 6 Sheets-Sheet 1Filed Nov. 25. 1964 Phillip Qi- Qoehri. 6 a, cflwg sffi Nov. 28, 1967 J,ROEHRIG 3,354,588

WIDE BELT ABRASIVE MACHINE Filed Nov. 25. 1964 e sheets-sheet 2 WQoehr'i a 710mm Nov. 28, 1967 J, OEHRIG 3,354,588

WIDE BELT ABRASIVE MACHINE Filed Nov. 25, 1964 6 SheetsSheet 5 z i W pkW "P Oew'i 4 40% cflTToimosyf Nov. 28, 1967 P. J. ROEHRIG 3,354,588

WIDE BELT ABRASIVE MACHINE Filed Nov. 25, 1964 6 Sheets-Sheet 4 f a 9. ja a.

Nov. 28, 1967 Filed Nov. 25, 1964 RQEHRIG 3,354,588

WIDE BELT ABRASIVE MACHINE 6 Sheets-Sheet 5 I 0.41,. am oqfl'omny 6Sheets-Sheet 6 P. J. ROEHRIG WIDE BELT ABRASIVE MACHINE Nov. 28, 1967Filed Nov. 25, 1964 Q1 Q0634 w W phdhp 7 M,

United States Patent 3,354,588 WIDE BELT ABRASIVE MACHINE Phillip J.Roehrig, Rockford, Ill., assignor to Solem Machine Company, Rockford,11]., a corporation of Illinois Filed Nov. 25, 1964, Ser. No. 413,793 12Claims. (Cl. 51141) ABSTRACT OF THE DISCLOSURE As a work sheet is fedalong a table, an abrasive belt is supported in triangular form by threerolls, one pressing the belt against the passing workpiece, anotherbeing power driven and supported near one end for back and forthtransaxial tilting about a transverse pivot to produce edgewisewandering of the belt and maintain the same centered properly on thethree rolls. To control wandering, the outboard end of the drive roll issupported by an eccentric which is adjusted back and forth by areversible power actuator whose reverse cycles are of timed durationdetermined by the passing of one edge of the belt back and forth acrossa fluid jet. The roll that drives the belt has a surface layer formedwith radially disposed and angularly spaced slits which contribute toincreased driving traction.

This invention relates to a so-called wide-belt sanding machine of thetype in which an endless abrasive belt extends around and is supportedin a generally triangular shape by three substantially parallel androtatable rolls, namely, a pressure roll for pressing a transverse areaof the belt against a passing workpiece, a power driven roll for drivingthe belt, and a roll urged transaxially to tension the belt. To avoidobjectionable edgewise creeping of the belt, the tension roll is usuallytilted alternately in opposite directions to induce edgewise andcontrolled oscillation of the belt back and forth along the rolls tomaintain the belt in an average centered position on the rolls.

One object of the present invention is to achieve an improved beltcentering or tracking action by tilting the drive roll instead of thetension roll as has been the practice heretofore.

Another object is to provide for more effective response of the belt totilting of the drive roll by locating the axis of tilting at one end ofsuch roll.

A further object is to provide a novel mounting of the drive roll whichpermits of such tilting while rotary power is being transmitted theretoby a shaft rotatable about a fixed axis.

Still another object is to effect the drive roll tilting by a novelmechanism which is located at the outboard end of the roll, whichprovides for automatic back and forth tilting to provide for effectivetracking of the belt, and which is disposed within the path of travel ofthe belt so as to permit convenient edgewise removal and replacementthereof.

A further object is to incorporate in the tilting mechanism for thedrive roll a novel means for effecting manual tilting of the roll tocompensate for variations in the length of opposite side edge portionsof the belt.

Another object is to oscillate the abrasive belt back and forth by amechanism which, as compared to prior controls, is simpler inconstruction, requires a minimum tilt, and reduces the tension requiredto be maintained in the belt.

The invention also resides in the novel mounting of the drive roll, thenovel character of the tilting mechanism therefor, and the manner ofcontrolling the tilting of the roll.

Other objects and advantages of the invention will become apparent fromthe following detailed description taken in connection with theaccompanying drawings, in which FIGURE 1 is a side view, partially insection, of an abrading machine incorporating the novel features of thepresent invention.

FIG. 2 is a fragmentary perspective view.

FIG. 3 is a partial cross-sectional view of the drive roll and belt.

FIG. 4 is a side view, partially in section, along the line 44 of FIG.1.

FIG. 5 is a fragmentary sectional view taken along the line 5-5 of FIG.4.

FIG. 6 is a fragmentary section taken along the line 66 of FIG. 1.

FIG. 7 is a schematic view of the tracking control circuit of theinvention.

FIG. 7a is an enlarged view of a part of FIG. 7.

FIG. 8 is a sectional view of the tension roll support mechanism.

FIG. 9 is a sectional view of the self-centering bearing structure ofthe pressure roll taken along the line 9-9 of FIG. 5.

FIG. 10 is a fragmentary section of the belt position sensor taken alongthe line 101il of FIG. 5.

In the drawings, the invention is shown for purposes of illustrationincorporated in a conventional so-called wide belt sander for utilizingan endless and flexible abrasive belt 11 to rough and finish sand thetop surface of a work sheet 12 of wood, metal, plastic, etc., while thesame is supported on and advanced by a suitable conveyor along ahorizontal table 13 on the top of a rigid base 14. Rigid with andupstanding from one side of the base is a column 15 from which projectshorizontally and cantilever fashion a casting 16 which supports theusual rolls 17, 18 and 19 by which the belt is supported in a generallytriangular shape, driven at high speed, tensioned, and presseddownwardly against the passing workpiece. The rolls each comprise arelatively thick sleeve 21 of resiliently yieldable material such asfirm rubber covering and bonded to a rigid cylinder 22 fixed at oppositeends to a shaft somewhat longer than the cylinder.

Opposite ends of the shaft 23 of the pressure roll 19 are supported inself-alining bearings 24 (FIGS. 1 and 9) each having an outer race ringpressed into a ring 25 having an external surface 26 disposedeccentrically relative to the shaft 23. These eccentrics are journaledin parts 28 of the casting 16. Fixed to the outer ends of the eccentricsare sprockets 29 which mesh with chains 30 extending around sprockets 31and 32 also journaled on the frame plate. By turning a crank 33 fixed tothe shaft of the sprocket 32, the pressure roll may be raised andlowered in small increments to vary the pressure holding the beltagainst the work. The vertical position of the roll and therefore thedepth of cut to be taken is gaged with reference to a scale 34.

To tension the belt and thus provide proper driving engagement with thedrive and pressure rolls, the roll 18 is spaced a short distance abovethe work path and horizontally from the pressure roll and opposite endsthereof are yieldably urged away from the pressure roll, in thisinstance by compression springs 35. For this purpose, opposite ends ofthe shaft 36 of the roll are journaled in bearings mounted in housings37 (FIGS. 1 and 4) on the lower ends of elongated arms 38 suspended frompivots 39 supported by the casting 16 within the triangular path of thebelt.

Each of the springs 35 bears at one end against an abutment ring 41seated in a web 42 (see FIG. 8) of the casting 16 and at the other endagainst an abutment 43 threaded onto a rod 44 which at one end projectsthrough the abutment 41 and at the other end is pivoted on the 3 freeend of a short crank arm 45 fast on a shaft 46 carrying a gear 47 (FIG.4). By turning the exposed head 48 on a pinion 49 meshing with the gear(FIGS. 1 and 4),

the crank may be swung between the tensioning position shown in full inFIGS. 1 and to the position shown in full in FIG. 8. In the latterposition, the tension is released and the belt freed for easy removalfrom the rolls.

Between the pressure and tension rolls is the usual pressure shoe 81extending across the full width of the belt and rigidly mounted on thecasting 16 for vertical adjustment through suitable means (not shown)actuated by turning a hand wheel 82 (FIG. 1). The yieldable butaccurately located surface of the shoe presses the belt against the worksurface after the same has been rough sanded by the action of thepressure roll. A more accurate finish of the work surface is thusproduced.

The drive roll 17 is spaced well above the pressure and tension rolls soas to provide a large are a (FIG. 5), nearly 180 degrees in the presentinstance, of driving contact with the belt. For a purpose to more fullyappear later, the projecting end of the shaft 49 of the roll issupported adjacent the end of the roll in a self-alining andanti-friction bearing 51 (FIG. 4) disposed within a housing 52 with itsinner race ring secured to the shaft while the outer ring is pressedinto a hole 53 in the upper end of a standard 54 secured to the column15. The shaft end is thus supported for limited tilting about an axisextending transaxially of the shaft.

The roll 17 is driven by an electric motor 55 mounted on top of thecolumn 15. To accommodate the tilting of the roll shaft within thebearing 51, the extended end of the shaft 49 is coupled to the motorshaft 56 through the medium of a suitable universal coupling 57.

In accordance with the present invention, an anti-friction self-aliningbearing 58 (see FIG. 6) supporting the outboard end of the drive rollshaft 49 is mounted for vertical adjustment to effect a controlledtilting of the drive roll about a horizontal axis 59 (FIG. 5) defined bythe center plane of the bearing 51. In the present instance, suchtilting can be effected manually or automatically by separate actuationof two concentrics 61 and 62. arranged concentrically and supporting thebearing 58 as shown in FIGS. 6 and 7.

To the foregoing ends, the inner race ring of the hearing is fixed onthe shaft 49 through the medium of a sleeve 63 and a lock-nut. The outerrace is pressed into a ring 64 closed at opposite ends by plates 65 toform a housing around the bearing. The ring, thus adapted to turn aboutits axis 72 coacts with ball-bearings 67 and a follower ring 68 to formthe eccentric 61. For this purpose, these bearings separated by a spacer69 are pressed onto the ring 64 whose outer cylindrical surface 71 isdisposed eccentrically relative to the shaft, that is, its axis 72 isofiset a short distance I) from the shaft axis 66. The bearings 67 arepressed into the follower ring 68 which is disposed between axiallyspaced fianges 73 formed by the margins of the plates 65.

The second and manually adjustable eccentric is formed by the ring 68having a cylindrical external surface 74 whose axis 75 is offset fromthe shaft axis 66 on the same side as the first eccentric but a somewhatgreater distance 0. The surface 74 is journaled in the surroundingstationary ring 76 straddled by radial flanges 77 and 78 at oppositeends of the eccentric ring. The ring 76 is formed on the upper end of apart 79 of the frame casting 16 upstanding just beyond the outboard endof the drive roll.

With the outboard end of the drive roll supported by the two eccentrics61, 62, it will be apparent that turning of the outer eccentric ring 68in opposite directions about its fixed axis 75 will raise and lower oneend of the shaft 49 whose axis 66 travels along an arcuate path 84 (FIG.7a) but through a short are disposed half above and half below ahorizontal plane 89 through the axis 75. Such adjustment of the shaft,being vertical and transversely of the long are a of contact between thebelt and the drive roll 17, produces a maximum amount of edgewiseshifting of the belt for a given amount of tilt of the roll by eitherone of the eccentrics 61, 62.

Tilting of the roll 17 by the outer eccentric 62 is made manually aftera new belt has been installed or after uneven stretching of a belt inservice use and for the purpose of compensating for a difference in thelengths of opposite side edge portions of the belt. To accomplish this,gear teeth 85 (FIG. 6) are formed around the periphery of the flange 77on the eccentric ring 68 and meshed with a pinion 86 fast on a headedstud 87 which is journaled on a clamping screw 88 threaded into thesupport ring 76. After loosening the screw, the stud may be turned by awrench applied to the head and the eccentric turned to correspondinglyvary the transaxial position along the path 84 of the outboard end ofthe drive roll thus equalizing the tension in opposite side edges of thebelt. After the adjustment, the screw is tightened so as to lock theeccentric in the selected position. It will be apparent that byemploying the eccentric type of adjustment, the amount of the tiltingcan be gaged accurately since the tilt is a very small part of theangular movement of the eccentric ring.

The automatic tilting of the drive roll to cause controlled edgewisewandering of the belt and maintain the same properly centered on thethree rolls is effected by rocking the eccentric ring 64 back and forthintermittently about its axis 72 whose position is fixed when theeccentric 62 is locked. In response to such rocking, the shaft axis 66traverses a short part, usually somewhat less than of an inch, of anarcuate path 91 whose radius is equal to the spacing b of the shaft andeccentric axes. As before, the range of the arcuate travel is preferablydisposed half above and half below the plane 89 and thereforetransversely of and about midway between the ends of the are a of beltand drive roll contact area.

Rocking of the eccentric 61 in opposite directions is effected in thepresent instance by selectively energizing two power actuators 92, 93(FIGS. 1 and 7) under the control of a single device 94 (FIGS. 7 and 10)for sensing edgewise shifting of the belt in opposite directions past apredetermined position 95 as a result of opposite tiltings of the driveroll. While the actuators may take various forms, the ones shown hereincomprise a cylinder 96 having a piston 97 slidable therein and fixed toa rod 98 disposed generally tangentially of the eccentric ring 64 withits outer end pivotally connected at 99 to a stud 101 projecting fromthe housing 65 parallel to the shaft 49 and near the periphery of thering. A yoke 102 (FIG. 2) projecting from the head end of the cylinderis pivoted at 103 on a stud 104 projecting from the end of the framecasting 16 within the triangular path traversed by the belt. Byemploying a reversible actuator of the rectilinear type and thuspositioned, it will be apparent that eccentric 61 may be oscillated backand forth within a range d (FIG. 7) in all angular positions of themanually adjustable eccentric 62. The relatively wide range of rockingof the eccentric 61 produces a substantially smaller movement, usuallysomewhat less than of an inch, of the outboard end of the drive rollthus enabling the tilting of the roll to be controlled with extremeaccuracy.

Preferably the sensing device 94 (see FIGS. 2, 5, 7 and 10) is arrangedto respond to changes in the position of the edge 105 of the belt at theinboard ends of the rolls and between the tension and drive rolls. Theoperating parts are supported by and enclosed in a housing 106 securedto a bracket 107 projecting from the arm casting 38. The device includesa nozzle 108 communicating with a source 109 of compressed air fordetecting a jet of air perpendicular to the path of edgewise travel ofthe belt along the supporting rolls. When the jet is unobstructed asshown in FIG. 10, the air passes through a hole 111 in the housing 106and impinges against a disk 112 on the free end of an arm 113 of aswitch 114 in a casing mounted within the housing 106. The switch whichis urged open by a spring 115 is thus held closed completing a circuit116 for energizing a solenoid 117 whose armature is on the outwardlyprojecting end of the plunger 118 of a reversing air valve 119.

When the jet is unobstructed by the belt as shown in FIG. 7, the switch114 is closed, the solenoid is energized, and the plunger is shifted tothe position shown for admitting compressed air from a supply line 109to a line 121 leading to the head end of the cylinder 96 through a checkvalve 122 which opens automatically. At this time, the rod end of thecylinder is connected through an unobstructed line 123 and the valve toa low pressure area 124. Thus, when the switch becomes closed by thebelt uncovering the air jet in moving in the direction of the full arrowin FIG. 7, the actuator 92 formed by the piston 7 and the head end ofthe cylinder 96 is energized and the eccentric 61 is shifted rapidlythrough the range d to the end 125 thereof. As a result, the outboardend of the drive roll 17 is moved rapidly through the full tilting rangee (FIG. 7a) thus reversing the direction of edgewise creeping of thebelt. Such creeping in the direction of the dotted arrow (FIG. 7)continues at a relatively rapid rate so long as the drive roll is heldin the new tilting position or tilted in such direction sufficiently toinduce the shifting of the belt to continue.

In the initial part of this reverse belt shifting, the edge 105 of thebelt passes the air jet and intercepts the latter thus permitting thespring 115 to open the switch 94, deenergize the solenoid, and reversethe position of the valve plunger 118 thus admitting high pressure airinto the rod end of the cylinder 96 while connecting the head end to thelow pressure are-a 124 through the passage 121 which includes aby-passage 126 controlled by a needle valve 127 adjusted to restrict andslow the outflow of air from the cylinder. The actuator 93 formed by thepiston and rod end of the cylinder 96 is thus energized to initiatereverse tilting of the roll but the creeping beyond the jet continuesuntil the belt reaches the other limit of the tilt range, the eccentricring 64 then being at the end 125 of the range d. Then, when the roll,in its mverse movement, passes the center of the range and the tiltingis reversed, the direction of creeping is reversed and the edge 105 ofthe belt starts to move back toward the jet. This movement continuesuntil the jet becomes uncovered causing the switch 114 to be closed andthe actuator 92 to be reenergized to again cause rapid movement of theeccentric ring 64 to the limit 125 in the manner described above.

As a result of the alternate reversals of the valve 119 and theaccompanying rapid and slow tilting of the drive roll 17, the belt isoscillated back and forth along the rolls within a range considerablynarrower and more positively controlled than has been possibleheretofore. By tilting the drive roll about one end, the belt is morereactive to the tilting with the result that the tendency of the belt toflutter or become rippled during the tracking action is reducedconsiderably. This not only prolongs the service life of the belt butalso makes for greater uniformity in the finished work surface.

It will be apparent from the foregoing that the eccentrics for manuallyand automatically tilting the drive roll as well as the supports for thetension roll and the means for adjusting the same are'all disposedwithin the triangular path traversed by the belt and are easilyaccessible from the outboard end of the supporting casting 16. All ofthe adjustments required in service use may be made easily from one endof the machine. During service operation, the free end of the casting 16is preferably clamped rigidly to the base 14 by a bar 131 (FIG. 2.)spanning side rails 132 on the top of the base and clamped to the latterand the free end of the casting by screws 133. These are loosened andthe bar removed when it is desired to replace a worn out belt. As apreliminary to this, the tension is relieved by drawing the roll 18inwardly to the position shown in full in FIG. 8. The belt may then bedrawn edgewise off from the three rolls and the shoe 81. Aftersubstituting a new belt, the roll 18 is swung outward to tension thebelt after which the eccentric 62 is adjusted to tilt the drive roll andequalize the tension at opposite side edges of the belt.

It will be apparent from the foregoing that the eccentrics automatictilting of the drive roll 17 through the eccentric 61 as above describedmay be increased and the range of edgewise shifting by the belt toachieve the desired centering or tracking may be reduced considerably bya simple modification of the surface of the drive roll to increase thetraction between this roll and the belt. To this end, the rubber orother resiliently yieldable material forming the surface layer 21 of theroll is slitted along parallel lines 134 (FIGS. 2 to 5) closely spacedangularly around the roll and extending longitudinally thereof butterminating at 135 short of the side edges of the belt in all edgewisepositions of the latter. The slits are simple straight cuts aboutone-eighth of an inch deep made by pressing a thin and sharp blade intothe rubber and drawing the same along the roll. The slits are spacedabout one inch apart and opposite side walls thereof are left in face toface contact since none of the material of the surface layer is removedin the slitting process. The outer portion of the yieldable layer 21 isdivided into segments which are flexible circumferentially of the roll.

It is believed that the improved traction resulting from such slittingof the drive roll is attributable to the differenial distortion of theareas 136, 137 on the leading and trailing sides of the slits 134 underthe forces to which these areas are subjected during high speed rotationof the roll within the tensioned belt. It is believed that the rubberareas 136 trailing the slits become compressed and denser as illustratedby the shading in FIG. 3 and push forward against the trailing walls ofthe slits thus causing the areas 137 to be forced outwardly and increasethe contact pressure between these areas and the belt. A noticeableincrease in the driving friction is observed through the use of theslits. By confining the slits to the area of the roll 17 which is alwaysdisposed between the side edges of the belt, the forces resulting fromradial compression of the areas 137 are transmitted forwardly to expandthese areas rather than being applied uselessly to distort the areaslongitudinally.

I claim as my invention:

1. In a Wide belt abrading machine having, in combination, an endlessbelt, a roll disposed within said belt for pressing a transverse area ofthe belt against a passing workpiece, a roll within the belt parallelingthe pressure roll and adapted to drive the belt, a roll within the beltparalleling said pressure and drive rolls and adapted for bodilytransaxial adjustment to tension the belt around the rolls, aself-alining bearing supporting one end of said drive roll for tiltingof the roll about a transverse axis perpendicular to the roll axis anddisposed substantially in the plane of said bearing, a power drivenshaft mounted outwardly beyond said transverse axis for rotation about afixed axis approximately alined with the drive roll axis, and auniversal coupling connecting said shaft and the end of said drive rollfor transmitting rotary power to the roll while permitting tilting ofthe roll about said transverse axis during such rotation.

2. An abrading machine asde-fined in claim 1 in which said drive roll isspaced a substantial distance from said' pressure and tension rolls toprovide for driving contact between the belt and drive roll over an arcof substantially a half revolution, and mechanism for moving theoutboard end of said drive roll alternately back and forth andcorrespondingly tilt the roll about said axis and along a path disposedintermediate the ends of said arc.

3. An abrading machine as defined in claim 1 including a secondself-alining hearing supporting the opposite end of said roll, meanssupportingv said second bearing for bodily transaxial shifting to tiltthe roll about said axis.

4. An abrading machine as defined in claim 3 including a device forsensing edgewise shifting of the belt to opposite limits of a narrowtracking range, and means controlled by said device for shifting saidsecond bearing alternately in opposite directions about said axis.

5. In a wide belt abrading machine having, in combination, an endlessbelt, a pressure roll disposed within said belt for pressing atransverse area of the belt against a passing workpiece, a drive rollwithin the belt paralleling the pressure roll and adapted to drive thebelt, said drive roll having first and second shaft ends, a tension rollwithin the belt paralleling said pressure and drive rolls and adaptedfor bodily transaxial adjustment to tension the belt around the rolls, aself-aligning bearing supporting said first shaft end for tilting of thedrive roll about a transverse axis perpendicular to the drive roll axis,means for transmitting rotary power to said first shaft end Whilepermitting tilting of the drive roll about said transverse axis duringsuch rotation, a second self-aligning bearing supporting said secondshaft end, an eccentric ring surrounding and rotatably supported by saidsecond bearing and having a cylindrical periphery with its axisparalleling but ofiset from the axis of said shaft ends, a secondnormally stationary ring in which said eccentric ring is supported toturn about its axis whereby to shift said second end transaxially tothereby tilt said drive roll about said first axis.

6. An abrading machine as defined in claim in which said second ring isjournaied on and rotatable relative to said eccentric ring and formedwith a cylindrical outer surface whose axis is offset laterally fromsaid shaft and eccentric axes, and a stationarily mounted ring in whichsaid second ring is journaled for rotation to swing said first eccentriring and said shaft about the axis of the stationary ring.

7. In a wide belt abrading machine having, in combination, an endlessbelt, a pressure roll disposed within said belt for pressing atransverse area of the belt against a passing workpiece, a drive rollwithin the belt paralleling the pressure roll and adapted to drive thebelt, said drive roll having first and second shaft ends, a tension rollwithin the belt paralleling said pressure and drive rolls and adaptedfor bodily transaxial adjustment to tension the belt around the rolls, aself-aligning bearing supporting said first shaft end for tilting of thedrive roll about a transverse axis perpendicular to the drive roll axis,means for transmitting rotary power to said first shaft end whilepermitting tilting of the drive roll about said transverse axis duringsuch rotation, a stationary support ring beyond the opposite end of saiddrive roll and having a cylindrical internal surface, an eccentric ringjournaled in said support ring surface for turning about an axis offsetlaterally from the axis of said drive roll, a second eccentric ringjournaled in said first eccentric ring to turn about an axis offsetlaterally from said drive roll axis and also the axis of said firsteccentric ring, a second self-aligning bearing supporting said secondshaft end and supported by and within said second eccentric ring, andindependently operable means for turning the respective eccentric ringswhereby to move said second bearing transaxially and thereby tilt saiddrive roll correspondingly.

8. In a wide belt abrading machine. having, in combination, an endlessbelt, a pressure roll disposed within said belt for pressing atransverse area of the belt against a passing workpiece, a drive rollwithin the belt paralleling the pressure roll and adapted to drive thebelt, said drive roll having first and second shaft ends, a tension rollwithin the belt paralleling said pressure and drive rolls and adaptedfor bodily transaxial adjustment to tention the belt around the rolls, aself-aligned bearing supporting said first shaft end for tilting of thedrive roll about a transverse axis perpendicular to the axis of thedrive roll, means for transmitting rotary power to said first shaft endwhile permitting tilting of the drive roll about said transverse axisduring such rotation, a stationary support beyond said drive rollopposite said axis, an eccentric journaled on said support to turn aboutan axis offset laterally from said drive roll axis, a second eccentricjournaled in said first eccentric to turn about an axis offset laterallyfrom said drive roll and first eccentric axes, a self-aligning bearingdisposed within and supported by said second eccentric and supportingsaid second shaft end for independent rotation of the drive roll, andindependently operable means for angularly adjusting the positions ofsaid first and second eccentrics, the position of said drive roll beingdetermined by the combined positions of the two eccentrics.

9. An abrading machine as defined in claim 8 including manually operablemeans for adjusting and holding the angular position of one of saideccentrics, a device operatively associated with one edge of said beltand operable to detect movement of such edge in opposite directions toopposite limits of a predetermined tracking range, and mechanismcontrolled by said device to move the other of said eccentricsalternatively in opposite directions.

10. In a wide belt abrading machine having, in combination, an endlessbelt, a roll disposed within said belt for pressing a transverse area ofthe belt against a passing workpiece, a roll within the belt parallelingthe pressure roll and adapted to drive the belt, a roll within the beltparalleling said pressure and drive rolls and adapted for bodilytransaxial adjustment to tension the belt around the rolls, meanssupporting said drive roll for back and forth tilting about a transverseaxis to induce edgewise oscillation of said belt, mechanism associatedwith the mounting of said drive roll for automatically tilting the sameback and forth about said axis between first and second positions, saidmechanism comprising one actuator adapted when activated to tilt thedrive roll quickly and uninterruptedly to said first position andthereby initiate shifting of the belt edgewise in a correspondingdirection, a second actuator adapted when activated to urge the driveroll in the opposite direction and toward said second position at a slowand restricted rate, and a device for sensing changes in the edgewiseposition of said belt and operating to activate said first actuator whenthe roll reaches said second position by the action of said secondactuator when said roll, while being tilted in the opposite direction bysaid first actuator, moves away from said second position.

11. An abrading machine as defined in claim 10 in which said firstactuator is unrestrained in its movement and the second actuatorincludes means for controllably restraining the motion of the actuator.

12. An abrading machine as defined in claim 10 in which said actuatorscomprise a cylinder, a piston reciprocated therein and coupled to saiddrive roll, and a valve and passages controlled by said sensing devicefor admitting pressure fluid to opposite ends, one of said passagespermitting the free flow of pressure fluid therethrough while the otherpassage includes a restriction for limiting the fiow of fluidtherethrough.

References Cited UNlTED STATES PATENTS 2,592,581 4/1952 Lorig. 2,597,2565/1952 Murray. 3,008,276 11/1961 Kile 51135 X 3,110,989 11/1963 Dawson51-435 3,153,306 10/1964 Robischung 51-135 ROBERT C. RIORDON, PrimaryExaminer.

D. G. KELLY, Assistant Examiner.

1. IN A WIDE BELT ABRADING MACHINE HAVING, IN COMBINATION, AN ENDLESSBELT, A ROLL DISPOSED WITHIN SAID BELT FOR PRESSING A TRANSVERSE AREA OFTHE BELT AGAINST A PASSING WORKPIECE, A ROLL WITHIN THE BELT PARALLELINGTHE PRESSURE ROLL AND ADAPTED TO DRIVE THE BELT, A ROLL WITHIN THE BELTPARALLELING SAID PRESSURE AND DRIVE ROLLS AND ADAPTED FOR BODILYTRANSAXIAL ADJUSTMENT TO TENSION THE BELT AROUND THE ROLLS, ASELF-ALINING BEARING SUPPORTING ONE END OF SAID DRIVE ROLL FOR TILTINGOF THE ROLL ABOUT A TRANSVERSE AXIS PERPENEDICULAR TO THE ROLL ANDDISPOSED SUBSTANTIALLY IN THE PLANE OF SAID BEARING, A POWER DRIVENSHAFT MOUNTED OUTWARDLY BEYOND SAID TRANSVERSE AXIS FOR ROTATION ABOUT AFIXED AXIS APPROXIMATELY ALIGNED WITH THE DRIVE ROLL AXIS, AND AUNIVERSAL COUPLING CONNECTING SAID SHAFT AND THE END OF SAID DRIVE ROLLFOR TRANSMITTING ROTARY POWER TO THE ROLL WHILE PERMITTING TILTING OFTHE ROLL ABOUT SAID TRANSVERSE AXIS DURING SUCH ROTATION.